Migraine Sufferers Face Greater Blood Clot Risk

MONDAY Sept. 15, 2008 -- Migraine patients face a higher risk for developing a blood clot in their veins, a team of Austrian and Italian researchers reports.

Prior studies have suggested that the absolute risk for a resulting stroke among migraine patients is actually quite low, but the current work turns conventional wisdom on its head by suggesting that a migraine diagnosis raises the risk for such potentially fatal clotting incidents -- known as venous thrombosis or thromboembolism -- while having little or no impact on the risk for developing any hardening or narrowing of the arteries.

"Our study refutes the widespread view that migraine [patients] are more likely to have hardening and narrowing of the arteries, [known as] atherosclerosis," noted study co-author Dr. Stefan Kiechl, from the department of neurology at Innsbruck Medical University, in Austria. "Alternatively, it suggests that migraine patients are more prone to develop blood clots in their veins."

"Because people that develop clots in [their] veins are also at an increased risk to develop clots in the arteries supplying brain and heart, our finding may in part explain the excess risk of stroke and heart attacks in migraine patients," Kiechl added.

Kiechl and his colleagues from Bruneck Hospital in Italy are publishing their findings in the Sept. 16 issue of Neurology.

The conclusions stem from an analysis of heart disease and neurological data collected in 2005 from 574 men and women living in Bruneck, a small village in the alpine region of northern Italy.

All the residents had been participating in an ongoing neurological study since 1990, and all were white and between the ages of 55 and 94.

After taking note of the residents' migraine history by means of a "headache interview," the researchers conducted high-resolution arterial ultrasounds and medical record reviews to look for evidence of either venous thrombosis clotting and/or hardening of the arteries.

The authors found that having migraines appeared to raise the risk for experiencing a blood clot in the veins. Among the 111 participants (23 men and 88 women) who had been diagnosed with a migraine at some point in their lives, almost 19 percent had experienced one or more instances of venous thrombosis. By comparison, the researchers noted that among those who had no history of migraines just under 8 percent had experienced the blood clotting condition.

About 80 percent of the recorded clot "events" were found to have coincided with an active migraine incident, the team noted.

Furthermore, the researchers observed that, contrary to popular thinking, having a history of migraines in no way raised the risk for developing a hardening of the arteries. In fact, they noted that atherosclerosis actually appeared to be less pronounced among migraine patients.

Although Kiechl and his associates theorized that the blood of migraine patients might be more susceptible to clotting, the researchers have not yet identified the underlying mechanism linking migraines with blood clot risk.

"Further studies are required to confirm our findings and explore why this is the case, and what can be done against it," Kiechl said.

Meanwhile, Dr. Rose Dotson, a clinical associate professor of neurology at Case Western Reserve Medical School and a neurologist at University Hospital's Case Medical Center in Cleveland, said she viewed the findings as having great importance.

"We have known for quite some time that people who have migraines are more prone to having strokes," she noted. "But this study gives us new and exciting information about this very real concern, which will change how we're going to look at migraine patients, how we're going to evaluate them, and how we're going to counsel them."

"Of course, we need to figure out exactly why these patients are having these clots," Dotson added. "But already this work moves us along with our understanding of the problem."